Selective catalytic cracking process of natural gas liquid fraction to light olefins and other products

ABSTRACT

A selective catalytic cracking process of natural gas liquid fraction to light olefins and other products is described, the process includes placing in contact (within a reaction zone) said liquid fraction of natural gas, rich in C 5   +  paraffins, with an MFI type zeolitic catalyst in acid form, having a pore size of at least 4 Angstroms, a silica/alumina ratio of between 10 and 2000, and where the processing conditions involve a temperature of between 350° C. and 650° C., space velocity of between 2 and 100 h −1  and atmospheric pressure, and afterwards carrying out the catalytic cracking to separate products, to recover a product enriched with light olefins, LPG fractions, and aromatics, and where the production of olefins is favored in conditions of higher space velocities, while the production of LPG fractions and aromatics are favored in conditions of lowered space velocities.

SCOPE OF THE INVENTION

The present invention belongs in the field of the catalytic crackingprocesses, more particularly, of the catalytic cracking of condensednatural gas fraction (C₅ ⁺) to obtain light olefins and the otherpetrochemicals, such as the GLP fraction and aromatics. The process iscarried out in the presence of an MFI type zeolitic catalyst in acidform.

FUNDAMENTALS OF THE INVENTION

The increasing necessity to preserve the environment as well as thesearch for fuels with lower particulate emission and gaseous pollutantssuch as nitrogen oxides (NOx), carbon dioxide (CO₂) and, chiefly, carbonmonoxide (CO), increases the demand for light olefins, which are used inthe alkylation processes to obtain higher octane fuel and in thesynthesis processes of oxygenated fuels, such as MTBE, ETBE and DME, asmentioned in articles by Buchanan, J. S., Catalysis, Today, 55, (2000),207-212, J. H Lunsford, Catalysis Today, 2000, 63, 165 and in Ullmann's,Encyclopedia of Industrial Chemistry, VA 8, ed. VCH., p. 541.

Moreover, the polymerization processes used to manufacturethermoplastics such as polyethylene and polypropylene, which use ethaneand propane, respectively, as raw material, also contribute to theincrease of demand for light olefins.

These basic petrochemical raw materials are traditionally produced bycracking naphtha. However, the strong growth in the world-wide demandfor these raw materials that occurred between 1990-1997, made the searchfor new production methods extremely important, especially for propane,the generation of which (by cracking naphtha) is less than theconsumption by petrochemical industries. Forecasts carried out by theBrazilian Association of Chemical Industries (ABIQUIM) indicate that, inBrazil, the offering of light olefins produced by refining naphthafractions will begin to be lower than the demand, from an optimisticviewpoint, starting in the year 2006, in accordance with the ABIQUIMEconomic Commission's Annual Report: “Demand for Petrochemical RawMaterials and Probable Origin up until 2010”, Otto V. Perrone, Carlos A.Daccache, Leonidas C. de M. Filho, Lucy H. M. N. Santos, Marcelo Wasemand Suzana Tintner, December/2002.

The world-wide offering of natural gas is not only increasing due to thedecline of petroleum reserves,.but also due to the fact that existingnatural gas reserves are not concentrated in the Middle East, as in thecase of petroleum.

Natural gas has occupied an ever increasing position of importance andwith a view towards an increase in demand during the next decades of the21 ^(st) century. As a consequence of fluctuations in price on the worldnaphtha market, the search for alternative routes using natural gas toobtain petrochemical supplies has been increasing.

When natural gas arrives at the Natural Gas Processing Units (NGPU), itundergoes compression or absorption processes, through which, at theend, processed natural gas fractions (C₁-C₂), LPG (C₃-C₄) are obtained,as well as condensed natural gas fractions (C₅ ⁺), also known as naturalgasoline. The LPG is basically used as residential gas, according toMoutinho dos Santos, E.; Zamalloa, G. C.; Villanueva, L. Dondero; Faga.;M. T. Werneck; “Natural Gas: Strategies for New Energy in Brazil”,ANNABLUME Publishing Company, 1^(st) edition, August/2002.

Natural gas generates 60% of the LPG produced in the world, while, inBrazil, this percentage is only 15%, according to the Annual Report ofthe BNDES Chemical Complex: Natural Gas as Raw Material for theProduction of Ethene in the State of Rio de Janeiro”, Montenegro, R.S.P.and Koo Pan, S. S, 2000.

The C₅ ⁺ fraction is rich in saturated hydrocarbons such as pentanes,hexanes and heptanes and is of low commercial value. Normally, it isincorporated into gasoline to adjust the vapor pressure of same while atthe same time it is mixed into crude oil to facilitate pipelinedraining. With the increase in the use and production of natural gas,this fraction has become extremely important from the business point ofview.

Zeolitic materials, both natural and synthetic, are known for theircatalytic properties in reactions with hydrocarbons, where they areused, for example, in cracking, hydrocracking, hydroisomerization,methanol production of gasoline, xylene isomerization, ethylbenzenesynthesis, hydrocarbon oxidation processes, etc. See the article on thissubject by Cusumano, J., Perspectives in Catalysis, J. M. Thomas and K.Zamarev (eds.), IUPAC, Chemistry for 21st Century, Blackwell ScientificPublication, 1992.

Typically, zeolites are porous crystalline aluminosilicates having adefined structure with cavities interconnected by channels. Thedimensions of the cavities and channels in the structure of thesematerials are within a range of 3 to 13 Å. These are typical diametermeasurements of organic molecules, which allow selective separation ofhydrocarbons, by using those known as molecular sieves, in accordancewith the publication by Breck, D. W. and Krieger, Robert E., MolecularZeolite Sieves, Publishing Company, Malabar, Flowery (1984). Zeolitesare classified by the type of topology its crystalline grid presents,without taking in consideration its composition, the distribution of thevarious tetrahedral atoms, the dimensions of unitary cells and symmetry.

One type of zeolite that is often utilized in catalytic crackingprocesses of gas oil, (as in the article mentioned above by Buchanan, J.S., Catalysis, Today, 55, (2000), 207-212), and in the production ofolefins from methanol, (see article by Olah, G. and Molnar A.,Hydrocarbon Chemistry, ed, John Wiley & Sons, Ina, 1995, P. 88) is theMFI type, a crystalline solid with a structure that includes pores of anaverage diameter ranging between 4 and 7 Å. The opening of the porescontains 10 atoms of oxygen.

One MFI zeolite that is quite well known for its high stability and forpresenting low coke formation is ZSM-5. See the article on this subjectby H. van Koningsveld, J. C. Jansen and H. van Bekkum, Zeolites, (1990),10, 235.

Many publications mention the use of zeolites of the MFI type, inisomerization reactions from linear olefins C₂-C₁₀ to olefinic productsC₄-C₇, such as for example, in patent EP-A-0026041.

Other patents, such as for example, U.S. Pat. No. 6,118,035, U.S. Pat.No. 6,566,293B1, and international publication WO 01/64761A2, alreadymention the use of MFI zeolites as additives in the FCC catalyticcracking process in a fluidized bed (Fluid Catalytic Cracking). See alsothe article by Buchanan, J. S., mentioned above, where increasing thereaction temperature favors an increase in selectivity of light olefins.

However, in another specific type of cracking process, known as DCC(Deep Catalytic Cracking), it is necessary to increase the temperatureand the vapor/oil ratio. However, thermal cracking is not veryselective, in which the formation of large amounts of products of lowercommercial value occur, like hydrogen, methane and ethane, as in U.S.Pat. No. 6,566,293 B1. The use of MFI type zeolites as conventionaladditives is also mentioned in some patents that normally include asource of phosphorous, as in the European patent application EP-A-511013and international publication WO 94/13754.

In other patent documents, the use of MFI type zeolites as additiveswhen mixed with zeolite Y is mentioned, as in U.S. Pat. No. 5,472,594,to obtain products with a high level of C₄-C₅ olefins or used as anadditive mixed to kaolin and phosphoric acid, as in U.S. Pat. No.5,521,133. However, the additives dilute the catalyst and lead to adecrease in conversion, as in U.S. Pat. No. 5,521,133.

It is well known that reaction models with n-hexane and 3-methyl-pentaneshow that the acid zeolites frequently have an important role inindustrial processes of paraffin catalytic cracking which are frequentlyused as reaction models in studies of the properties of zeolite acids,as according to the publications of P. Voog and H. Van Bekkum, AppliedCatalysis, 59, 1991, 3311-331 and of John Abbot, Applied Catalysis, 57,1990, 105-125.

Therefore, in spite of existing developments, the technique still needsa process of selective catalytic cracking on a MFI type zeoliticcatalyst where the load is the liquid C₅ ⁺ fraction of condensed naturalgas made up of mostly paraffins, to obtain light olefins and otherpetrochemical supplies such as the LPG fraction and aromatics. Saidcatalytic cracking process is described and claimed in the presentapplication.

SUMMARY OF THE INVENTION

In a broad sense, the process of selective catalytic cracking of theliquid fraction of natural gas to light olefins and other products inaccordance with the invention includes placing said liquid fraction ofnatural gas, rich in C5+ paraffins, in contact (within a reaction zone)with an MFI type zeolitic catalyst in acid form, having a pore size ofat least 4 Angstroms, a silica/alumina ratio of between 10 and 2000, andwhere the processing conditions involve a temperature of between 350° C.and 650° C., space velocity of between 2 and 100 h⁻¹ at atmosphericpressure, and afterwards carrying out the catalytic cracking to separateproducts, to recover a product enriched with light olefins, LPGfractions and aromatics, and where the production of olefins is favoredin conditions of higher space velocities, while the production of LPGfractions and aromatics are favored in conditions of lowered spacevelocities.

Thus, the invention proves a selective catalytic cracking process ofcondensed natural gas fraction to obtain light olefins, LPG andaromatics.

Moreover, the invention proves a selective catalytic cracking process ofcondensed natural gas fraction to obtain light olefins, LPG andaromatics in the presence of an MFI type catalyst.

The invention also proves an MFI type catalyst to be used in saidselective catalytic cracking process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One aspect of the invention deals with a selective catalytic crackingprocess of the condensed fraction of natural gas, rich in C₅ ⁺paraffins, in the presence of an MFI type catalyst in acid form, with asilica/alumina ratio of between 10 and 2000, preferably of between 50and 500, even more preferably of between 20 and 100, at a temperature ofbetween 350° C. and 600° C., preferably at 530° C., and at a spacevelocity of between 2 and 100 h⁻¹, and afterwards to carry out thecracking, to recover a product enriched with light olefins, LPGfractions, and aromatics.

The useful load for the process of the invention is a condensed naturalgas rich in C₅ ⁺ paraffins. Typical compositions of the condensed loadare listed in the Tables corresponding to Examples 1, 2, and 3 below.

As is described, an example of the invention of a catalytic crackingprocess is performed at laboratory scale. The conditions adopted forspace velocity (WHSV) are those used for natural condensed gas loadinjection at atmospheric pressure. Catalytic tests have a duration ofapproximately 24 hours.

The reaction temperature applied during our catalytic tests waspreferably at 530° C., but the process is equally operational at ahigher range of temperature, between 350° C. and 650° C.

The catalytic test unit is coupled with a gas chromatographer equippedwith a Plot KCI/Al₂O₃ capillary column with 50m to identify theproducts.

The load of natural condensed gas is maintained with a continuous streamon a catalyst mass for a period of approximately 24 hours.

The operational conditions used in the catalytic tests are described inour Examples 1, 2, and 3.

In another aspect, the invention deals with a useful MFI catalyst in thepresent process of selective catalytic cracking.

Thus, zeolites with an average pore size that is useful for theinvention are described in “Atlas of Zeolite Structure Types”, eds. W.H. Meier and D. H. Olson, Butterworth-Heineman, Third Edition, 1992.

Zeolites with an average pore size exhibit a pore size of between 5 and7 Angstroms and include, for example, zeolites with an MFI, MFS, MEL,MTW, EUO, MTT, HEU, FER, and TON structure. Non-restrictive examples ofthese zeolites of average pore size include ZSM-5, ZSM-12, ZSM-22,ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, ZSM-50, silicalite, andsilicalite 2. Other zeolites of average pore size include theSilico-Aluminophosphate (SAPO), as SAPO-4 and SAPO-11, Chromosilicates,Gallium Silicates, Silicates of Iron; Aluminum Phosphates (ALPO), asALPO-11, Titanium Aluminosilicates (TASO), as TASO-45; Boron Silicates;Aluminophosphate of Titanium (TAPO), as TAPO-11; and Aluminosilicates ofIron.

An especially useful catalyst for the practice of the invention exhibitsa zeolitic structure of the MFI type (called MFI), preferably containinga SiO₂/Al₂0₃ molar ratio of between 20 and 2000. The textural propertiesand the chemical analysis of this typical catalyst, are presented inTable 1, through the area specific (BET) and superficial resultsobtained. Additionally, the micropore and mesopore volume is determinedby nitrogen adsorption at 196° C. (T-Plot Method). The chemical analysisis determined by X-Ray fluorescence. From this analysis the SiO₂/Al₂O₃molar ratio is calculated. A preferred MFI zeolite catalyst is theZSM-5.

Although the following Examples have been produced using a specificcatalyst, it should be quite clear to specialists that other catalystsof the same type may be used.

Still, although the tests here reported will be performed using a purezeolite catalyst, on an industrial scale, it will be made up in theusual way with matrix, binder, etc.

Before using the catalyst, it is pre-macerated and sifted, having beenacquired by grain size distribution between 0.510 mm and 0.044 mm (20and 250 Tyler mesh), preferably between 0.247 mm and 0.091 mm (42 and115 Tyler mesh) to lower the incidence of any problems relative todiffusion control during the catalytic tests. On an industrial scale,the catalyst is used in the form of dust, pellet or any otherconfiguration.

The catalyst is pretreated at a temperature within the range of between200-650° C., preferably between 300-600° C., more specifically, 530° C.,for a period of 2 hours with a heating rate of 5° .C/min under thecontinuous flow of a carrier gas (preferably air or nitrogen) at 40ml/min. TABLE 1 Textural Analysis Specific Area (m²/g) 422 MicroporeVolume (cm³/g) 0.173 Mesopore Volume (cm³/g) 0.098 External Area (m²/g)53 Chemical Analysis (% p/p) SiO₂ 97.97 Al₂O₃ 2.035 Na₂O <0.005SiO₂/Al₂O₃ molar ratio of the grid 82

The textural properties and chemical composition of a catalyst adjustedfor the process of the invention are listed in Table 1.

The performance of the catalyst used in different operational conditionswas evaluated through the effluent's composition values (% weight) andfrom the calculations of selectivity (% weight) calculated from theresults obtained through the conventional chromatography technique inthe gaseous phase.

The terms used in the Example tables and the calculation of selectivity(% weight) are defined below:

-   1)—Total Olefins=Ethene (% weight)+Propene (% weight)+Butenes (%    weight)-   2)—LPG Fraction=Propane (% weight)+Butanes (% weight)-   3)—Total Aromatics (%)=Benzene (% weight)+Ethylbenzene (%    weight)+Toluene (% weight)+p and m-Xylene (% weight)+o-Xylene (%    weight) +1,2,3 Trimethyl Benzene (% weight)+1,2,4 Trimethyl Benzene    (% weight)+1,3,5 Trimethyl Benzene (% weight) $\begin{matrix}    {{Selectivity}\quad{of}\quad{products}{\quad{( {\% p} ) = \lbrack \frac{{Composition}{\quad\quad}{of}\quad{the}\quad{Product}\quad{( {\%\quad{weight}} ) \times 100}}{{Load}\quad{Conversion}} \rbrack}}} &  4 )    \end{matrix}$

The invention will be illustrated by the following Examples, whichshould not be considered restrictive.

In Example Tables 2, 3, and 4 show the results of the composition (%weight) of the effluent for the catalytic tests or Examples 1, 2, and 3,respectively, after 2, 12 and 24 hours of reaction.

Tables 5, 6, and 7 show the results of product selectivity (% weight)obtained for these same reaction times, respectively, for the tests orExamples 1, 2, and 3.

EXAMPLE 1

The catalyst used is an MFI type zeolite (called MFI). The catalyst ispre-macerated and sifted, having been acquired by grain sizedistribution between 0.247 mm and 0.091 mm (42 and 115 Tyler mesh). Itis pretreated at a temperature of 530° C. for 2 hours with a heatingrate of 5° C./min under a continuous flow at 40 ml/min, preferably withsynthetic air. The reaction takes place at a temperature of 530° C.

The load of natural condensed gas is maintained with a continuous streamat 0.599 ml/min on a catalyst mass of 0.2626 g (WHSV=85.10h⁻¹), for aperiod of approximately 24 hours. The performance of the catalyst isevaluated for the reaction times corresponding to 2, 12, and 24 hoursthat are shown in Table 2 through the result of the effluent composition(% weight) for the test in Example 1.

The calculated selectivity values (% weight) for these same reactiontimes are shown compiled in Table 5. TABLE 2 Composition (% Weight)Compounds Feed 2 H 12 H 24 H Methane — 0.3 0.3 0.2 Ethane — 0.6 0.7 0.6Ethene — 1.3 1.5 1.2 Propane — 2.4 2.7 2.1 Propene — 2.9 3.6 3.1Isobutane 0.2 0.6 0.6 0.4 n-Butane 9.9 11.2 8.2 9.3 trans-2-Butene — 0.50.6 0.6 1-Butene — 0.4 0.5 0.4 Isobutane — 0.9 1.1 1.0 cis-2-Butene —0.4 0.5 0.4 Isopentane 24.6 23.2 21.0 21.3 n-Pentane 28.2 25.3 24.2 24.0Pentanes — — — — C6 Sat + Insat 25.6 20.4 23.4 23.2 C7 Sat + Insat 8.26.2 7.1 8.8 C8 Sat + Insat 2.1 1.7 1.6 1.6 C9 Sat + Insat 0.2 0.2 — —Benzene 0.5 0.6 0.6 0.5 Toluene 0.4 0.9 1.0 0.8 Ethyl-Benzene — — 0.10.1 p and m-Xylene 0.1 — 0.5 0.3 o-Xylene — — 0.1 0.1 1,2,3Trimethylbenzene — — — — 1,2,4 Trimethylbenzene — — — — 1,2,3Trimethylbenzene — — — — Others — — — — Totals Olefins (%) (C2-C4) — 6.47.8 6.7 LPG Fraction (%) 10.1 14.2 11.5 11.8 Total Aromatics (%) 1.0 1.52.4 1.8 Load Conversion (%) 11.5 10.9 9.4H = hours;WHSV = 85.1 h⁻¹;Reaction Temperature = 530° C.

EXAMPLE 2

The catalyst used is an MFI type zeolite (called MFI). The catalyst ispre-macerated and sifted, having been acquired by grain sizedistribution between 0.247 mm and 0.091 mm (42 and 115 Tyler mesh). Itwas pretreated at a temperature of 530° C. for 2 hours with a heatingrate of 5° C./min under the continuous flow at 40 ml/min, preferablywith synthetic air. The reaction takes place at a temperature of 530° C.

The load of natural condensed gas is maintained with a continuous streamat 0.3020 ml/min on a catalyst mass of 0.5020g (WHSV=22.44 h⁻¹), for aperiod of approximately 24 hours.

Table 3 shows the result of the effluent composition (% weight) for thetest in Example 2, in which the performance of the catalyst is evaluatedfor the reaction times corresponding to 2, 12 and 24 hours. Thecalculated selectivity values (% weight) for these same reaction timesare shown in Table 6.

EXAMPLE 3

The catalyst used is an MFI type zeolite (called MFI). The catalyst ispre-macerated and sifted, having been acquired by grain sizedistribution between 0.247 mm and 0.091 mm (42 and 115 Tyler mesh). Itwas pretreated at a temperature of 530° C. for 2 hours with a heatingrate of 5° C./min under the continuous flow at 40 ml/min, preferablywith synthetic air. The load of natural condensed gas is maintained witha continuous stream at 0.1425 ml/min on a catalyst mass of 1.0133 g(WHSV-5.25 h⁻¹), for a period of approximately 24 hours. The performanceof the catalyst is evaluated for the reaction times corresponding to 2,12, and 24 hours.

The results of the effluent composition (% weight) for Test 3 are shownin Table 4.

The calculated selectivity values (% weight) for these same reactiontimes are shown in Table 7. TABLE 3 Composition (% Weight) CompoundsFeed 2 H 12 H 24 H Methane — 1.1 1.1 0.9 Ethane — 2.7 2.7 2.2 Ethene —3.8 3.6 3.2 Propane — 10.7 9.7 7.3 Propene — 7.2 7.0 6.3 Isobutane 0.12.4 2.1 1.5 n-Butane 16.8 10.9 10.6 11.7 trans-2-Butene — 1.2 1.2 1.11-Butene — 0.9 0.9 0.8 Isobutane — 2.1 2.0 1.8 cis-2-Butene — 0.9 0.90.8 Isopentane 30.7 16.3 16.5 19.0 n-Pentane 32.3 14.7 15.3 17.8Pentenes — 0.0 0.0 0.0 C6 Sat + Insat 17.0 11.8 12.9 12.4 C7 Sat + Insat2.3 3.2 3.7 3.5 C8 Sat + Insat 0.2 1.2 1.1 1.1 C9 Sat + Insat — 0.0 0.00.0 Benzene 0.3 1.2 1.2 1.1 Toluene 0.1 2.9 2.8 3.0 Ethyl-Benzene — 0.30.3 0.3 p and m-Xylene — 2.1 2.2 2.2 o-Xylene 0.2 0.7 0.7 0.7 1,2,3Trimethylbenzene — 0.1 0.1 0.0 1,2,4 Trimethylbenzene — 0.4 0.3 0.31,2,3 Trimethylbenzene — 0.2 0.2 0.2 Others — 1.0 0.9 0.8 Totals Olefins(%) (C2-C4) — 16.1 15.6 14.0 LPG Fraction (%) 16.9 24.0 22.4 20.5 TotalAromatics (%) 0.6 7.9 7.8 7.8 Load Conversion (%) — 37.2 35.3 30.8H = hours;WHSV = 22.44 h⁻¹;Reaction Temperature = 530° C.

TABLE 4 Composition (% Weight) Compounds Feed 2 H 12 H 24 H Methane —3.3 2.5 2.2 Ethane — 6.7 5.2 4.6 Ethene — 4.2 4.0 3.5 Propane — 22.317.9 14.5 Propene — 6.4 6.4 5.7 Isobutane 0.1 4.0 3.6 2.9 n-Butane 8.96.3 6.8 6.7 trans-2-Butene — 0.9 0.9 0.9 1-Butene — 0.6 0.7 0.7Isobutane 1.5 1.6 1.5 cis-2-Butene — 0.7 0.7 0.7 Isopentane 19.7 5.8 6.87.5 n-Pentane 29.8 3.0 4.1 4.9 Pentanes — 0.1 0.1 0.1 C6 Sat + Insat31.6 2.8 3.6 3.8 C7 Sat + Insat 8.1 0.6 1.3 1.3 C8 Sat + Insat 1.0 0.10.6 1.0 C9 Sat + Insat — 0.0 0.1 1.2 Benzene 0.5 3.7. 3.6 3.3 Toluene0.3 12.1 11.5 10.4 Ethyl-Benzene — 0.9 0.9 1.3 p and m-Xylene — 7.5 7.99.8 o-Xylene — 2.4 2.9 3.6 1,2,3 Trimethylbenzene — 0.4 0.5 0.7 1,2,4Trimethylbenzene — 0.7 1.1 1.7 1,2,3 Trimethylbenzene — 0.5 0.8 1.1Others — 2.5 3.9 4.4 Totals Olefins (%) (C2-C4) — 14.3 14.3 13.0 LPGFraction (%) 9.0 32.6 28.3 24.1 Total Aromatics (%) 0.8 28.2 29.2 31.9Load Conversion (%) — 77.1 73.4 71.8H = hours;WHSV = 5.25 h⁻¹;Reaction Temperature = 530° C.

TABLE 5 Conversion (% weight) 2 H 12 H 24 H 11.5 10.9 9.4 ProductsSelectivity (% Weight) Methane 2.4 2.1 2.2 Ethane 6.1 5.4 5.6 Ethene11.8 11.5 11., 7 Propane 22.7 20.6 19.3 Propene 27.2 27.4 29.5 Isobutane4.5 2.9 2.2 trans-2-Butene 4.8 4.9 5.2 1-Butene 3.5 3.6 3.8 Isobutane8.2 8.4 8.9 cis-2-Butene 3.6 3.7 4.0 Benzene 0.9 1.2 0.9 Toluene 4.2 4.03.9 Ethyl-Benzene 0.1 0.6 0.5 p and m-Xylene — 3.0 1.9 o-Xylene — 0.70.4 1,2,3 Trimethylbenzene — — — 1,2,4 Trimethylbenzene — — 1,3,6Trimethylbenzene — — — Others — Total Olefins (%) 59.1 59.5 63.1 LPGFraction (%) 27.2 23.5 21.5 Total Aromatics (%) 5.2 9.5 7.6H = hours;WHSV = 85.1 h⁻¹;Reaction Temperature = 530° C.

TABLE 6 Conversion (% weight) 2 H 12 H 24 H 37.2 35.3 30.8 ProductsSelectivity (% Weight) Methane 2.7 2.7 2.6 Ethane 6.6 6.8 6.5 Ethene 9.29.3 9.5 Propane 26.0 24.7 21.7 Propene 17.5 17.9 18.5 Isobutane 5.7 5.04.1 trans-2-Butene 3.0 3.0 3.2 1-Butene 2.2 2.2 2.4 Isobutane 5.1 5.25.5 cis-2-Butene 2.2 2.3 2.4 Benzene 2.1 2.4 2.3 Toluene 6.7 6.9 8.6Ethyl-Benzene 0.7 0.9 1.0. p and m-Xylene 5.1 5.6 6.5 o-Xylene 1.1 1.21.3 1,2,3 Trimethylbenzene 0.3 0.2 0.0 1,2,4 Trimethylbenzene 0.9 0.91.0 1,2,3 Trimethylbenzene 0.6 0.6 0.7 Others 2.3 2.2 2.2 Total Olefins(%) 39.2 39.9 41.5 LPG Fraction (%) 31.7 29.7 25.8 Total Aromatics (%)17.1 18.7 21.3H = hours;WHSV = 22.44 h⁻¹;Reaction Temperature = 530° C.

TABLE 7 Conversion (% weight) 2 H 12 H 24 H 77.1 73.4 71.8 ProductsSelectivity (% Weight) Methane 4.1 3.3 3.0 Ethane 8.3 6.9 6.3 Ethene 5.35.3 4.8 Propane 27.7 23.6 19.9 Propene: 7.9 8.4 7.9 Isobutane 5.0 4.73.9 trans-2-Butene 1.1 1.3 1.2 1-Butene 0.8 0.9 0.9 Isobutane 1.9 2.22.1 cis-2-Butene 0.8 1.0 0.9 Benzene 4.0 4.0 3.9 Toluene 14.6 14.8 13.9Ethyl-Benzene 1.1 1.2 1.9 p and m-Xylene 9.3 10.4 13.5 o-Xylene 3.0 3.85.0 1,2,3 Trimethylbenzene 0.5 0.6 1.0 1,2,4 Trimethylbenzene 0.9 1.52.4 1,2,3 Trimethylbenzene 0.6 1.0 1.5 Others 3.1 5.1 6.0 Total Olefins(%) 17.8 19.1 17.8 LPG Fraction (%) 32.7 28.3 23.8 Total Aromatics (%)34.0 37.3 43.1H = hours;WHSV = 5.25 h⁻¹;Reaction Temperature = 530° C.

The present invention deals with a catalytic cracking process forselective production of olefins, especially light olefins (C₂-C₄) andother petrochemical supplies, such as, the LPG fraction(propane+butanes) and aromatics from condensed natural gas.

The products obtained from catalytic cracking of the fraction derivedfrom condensed natural gas were analyzed with composition values (%weight) and included, preferably, between 6% and 16% for total olefins,from 11% to 33% for the LPG fraction and from 1% to 32% for thearomatics.

Although the invention's illustrative examples use composition values in% weight of total olefins, LPG fraction and aromatics mentioned above,experts in the field will easily understand that these ranges may(according to different processing conditions) extend, with no problems,to include percentage values by weight, respectively, of between 2-50,preferably between 4-30, and even more preferably between 6-20 for totalolefins, between 5-70, preferably, 7-50, and still more preferably,9-40, for the LPG fraction, and between 1-50, preferably, 1-40, andstill more preferably, between 1-35, for the aromatics, without alteringthe scope of the present invention.

The processing data allows verification that the production of olefinsis favored under conditions of greater space velocities, whereas theproduction of the LPG fraction and aromatics is favored under lowerspace velocity conditions. Lower space velocities favor the productionof aromatics in the process, principally toluene.

The composition (% weight) of toluene falls within a preferable range ofbetween 33% and 44% of the total aromatic fraction composition.Calculated selectivity values (% weight) of the effluent in tests 1, 2,and 3, include values ranging preferably between 17% and 63% for totalolefins, from 21% to 33% for the LPG fraction and from 4% and 43% forthe aromatics.

In a way similar to the experimental values found for the percentage inweight of products, the selectivity values (in percentages in weight)may also be extended to greater ranges, depending on the processingconditions used. In the same way, experts may understand thatselectivity ranges, (always in percentages by weight) may be between10-80, preferably between 15-70, and even more preferably between 17-65,for total olefins, between 5-50, preferably between 10-40, and even morepreferably between 15-35, for the LPG fraction, and between 1-70,preferably between 3-60, and even more preferably between 5-45 for thearomatics.

1. Selective catalytic cracking process of natural gas liquid fractionto light olefins and other products, characterized in that it includesplacing said liquid fraction of natural gas, rich in C5+ paraffins, incontact (within a reaction zone) with an MFI type zeolitic catalyst inacid form, having a pore size of at least 4 Angstroms, a silica/aluminaratio of between 10 and 2000, and where the processing conditionsinvolve a temperature of between 350° C. and 650° C., space velocity ofbetween 2 and 100 h⁻¹ and atmospheric pressure, and afterwards carryingout the catalytic cracking to separate products, to recover a productenriched with light olefins, LPG fractions, and aromatics, and where theproduction of olefins is favored in conditions of higher spacevelocities, while the production of LPG fractions and aromatics arefavored in conditions of lowered space velocities.
 2. Process inaccordance with claim 1, characterized by the use of an MFI typezeolitic catalyst in the form of dust, pellet or any otherconfiguration.
 3. Process in accordance with claim 1, characterized inthat additional to before the use of said catalyst, it is pretreated ata temperature within the range of 200-650° C., preferably between300-600° C., more specifically at 530° C., for a period of 2 hours underthe continuous flow of a carrier gas (preferably air or nitrogen). 4.Process in accordance with claim 1, characterized in that the MFI typecatalyst is a ZSM-5 zeolite.
 5. Process in accordance with claim 1,characterized in that the results obtained of total olefins(ethene+propene+butenes) in the effluent with a composition (% weight)falls within a range of between 2% and 50%, preferably between 4% and30%, more preferably between 6% and 20%.
 6. Process in accordance withclaim 1, characterized in that the results of the LPG fraction in theeffluent with a composition (% weight) fall within a range of between 5%and 70%, preferably between 7% and 50%, more preferably between 9% and40%.
 7. Process in accordance with claim 1, characterized in that theresults of the aromatic fraction in the effluent with a composition (%weight) fall within a range of between 1% and 50%, preferably between 1%and 40%, more preferably between 1% and 30%.
 8. Process in accordancewith claim 7, characterized in that the composition (% weight) oftoluene falls within a preferable range of between 33% and 44% of thetotal aromatic fraction composition.
 9. Process in accordance with claim1, characterized in that the results of selectivity (% weight) for totalolefins (ethene+propene+butenes) fall within a range of between 10% and80%, preferably between 15% and 70%, more preferably between 17% and65%.
 10. Process in accordance with claim 1, characterized in that theresults of selectivity (% weight) for the LPG fraction fall within arange of between 5% and 50%, preferably between 10% and 40%, morepreferably between 15% and 35%.
 11. Process in accordance with claim 1,characterized in that the results of selectivity (% weight) for thearomatics fall within a range of between 1% and 70%, preferably between3% and 60%, more preferably between 5% and 45%.